• Mining
• Oil and gas extraction
• Manufacturing industries
• Petroleum manufacturing.
The main human activity that generates large amounts of nitric oxide is combustion in power plants, cars and trucks. High temperatures in internal combustion engines produce nitric oxide:
N2 (g) + O2 (g) → 2NO (g)
Reasons for concern
Health effects
Low levels of oxides of nitrogen can irritate eyes, nose, throat and lungs. This may possibly lead to coughing, shortness of breath, tiredness and nausea. Exposure to oxides of nitrogen can also result in a build up of fluid in the lungs for 1-2 days after exposure. High levels of oxides of nitrogen can cause rapid burning, spasms and swelling of tissues in the throat and upper respiratory tract, reduced oxygenation of tissues, and possibly even death.
Environmental effects
Excessive levels of the oxides of nitrogen, predominantly nitrogen dioxide (NO2), can cause death in plants and roots and damage the leaves of many agricultural crops. Nitrogen dioxide is the damaging component of photochemical smog, and also participates in ozone layer depletion. Excessive levels increase the acidity of rain, and thus lower the pH of surface and ground waters and soil. This in turn can have harmful effects, possibly even death, on a variety of biological systems.
When dissolved in rain, it forms acid rain:
2NO2 (g) + H2O (l) → HNO3 (aq) + HNO2 (aq)
Acid rain can damage the environment in many ways:
• The decay and deterioration of constructions and buildings particularly those made of calcium carbonate.
• Further ions, eg. aluminum – can be harmful to plant and animal life and these are locked in insoluble compounds. Soils that are acidic can boost this solubility, which releases toxic ions.
• Some plants cannot endure acidic soils. Its growth can be affected and also this can cause defoliation.
• A range of animals are sensitive to the acidity levels of their environment (especially rivers and lakes). The increase of acidity levels can affect their reproduction or even kill them.
• Hydrogen sulfate from the sulfuric acid can leak out vital plant chemicals from the soil.
Evaluation
• The release of oxides of sulphur and nitrogen must be controlled, as they are harmful not only to humans but also the environment. • The destruction of the natural environment can lead to a change in ecosystems. • The result of these oxides leads to acid rain which also damages the man-made environment resulting in financial costs. • Damage to vegetation and other animals can have various economic consequences. • Social costs of health problems related to these oxides are immeasurable.
